Raising of the Upper Boundary of Picea schrenkiana on the Moldo-Too Ridge Due to Climate Changes

The interannual net primary production variation and trends of a Picea schrenkiana forest were investigated in the context of historical changes in climate and increased atmospheric CO2 concentration at four sites in the Tianshan Mountain range, China. Historical changes in climate and atmospheric CO2 concentration were used as Biome–BGC model drivers to evaluate the spatial patterns and temporal trends of net primary production (NPP). The temporal dynamics of NPP of P. schrenkiana forests were different in the western, middle and eastern sites of Tianshan, which showed substantial interannual variation. Climate changes would result in increased NPP at all study sites, but only the change in NPP in the western forest (3.186 gC m−2 year−1, P < 0.05) was statistically significant. Our study also showed a higher increase in the air temperature, precipitation and NPP during 1987–2000 than 1961–1986. Statistical analysis indicates that changes in NPP are positively correlated with annual precipitation (R = 0.77–0.92) but that NPP was less sensitive to changes in air temperature. According to the simulation, increases in atmospheric CO2 increased NPP by improving the water use efficiency. The results of this study show that the Tianshan Mount boreal forest ecosystem is sensitive to historical changes in climate and increasing atmospheric CO2. The relative impacts of these variations on NPP interact in complex ways and are spatially variable, depending on local conditions and climate gradients.

The climate changed from warm-dry to warm-wet during the 1960s in northwest China. However, the effects of climate change on the response of radial growth from different age-class trees have been unclear. We assessed the age-effect radial growth responses in three age-classes (ml-old: ≥200 years, ml-middle: 100–200 years and ml-young: <100 years) of Schrenk spruce (Picea schrenkiana Fisch. et Mey.) in the eastern Tianshan Mountains. The primary conclusions were as follows: the developed chronologies of the three age-class trees contained significant climate information and exhibited high similarity as shown by calculating the statistical parameter characteristics and Gleichlaufigkeit index. The three age-class trees were consistent for annual variation trends of radial growth under climate change, showing similar fluctuations, tree-ring width chronology trends, time trends of cumulative radial growth, and basal area increment. In addition, the old and middle trees were found to be more sensitive to climate variability by analyzing Pearson correlations between radial growth from three age-class trees and climate factors. As a result, the drought caused by reduced total precipitation and higher mean temperature was a limiting factor of tree radial growth, and the trees with ages of up to 100 years were more suitable for studies on the growth-climate relationships. Thus, the studies on age-effect radial growth responses of Schrenk spruce can help not only in understanding the adaptive strategies of different-age trees to climate change, but also provide an accurate basis for climate reconstruction.

PDF HTML阅读 XML下载 导出引用 引用提醒 不同去趋势方法的新疆东天山高低海拔雪岭云杉树轮宽度年表对气候的响应 DOI: 10.5846/stxb201808231800 作者: 作者单位: 新疆师范大学地理科学与旅游学院,中国气象局乌鲁木齐沙漠气象研究所,中国气象局乌鲁木齐沙漠气象研究所,中国气象局乌鲁木齐沙漠气象研究所,中国气象局乌鲁木齐沙漠气象研究所,新疆师范大学地理科学与旅游学院,新疆师范大学地理科学与旅游学院 作者简介: 通讯作者: 中图分类号: 基金项目: 中亚大气科学研究基金（CAAS201814）；中国科学院战略性先导科技专项（XDA20100306）；国家自然科学基金（41675152，41805130）；中央公益性科研院所基本科研业务费（IDM2016006） The response of tree-ring chronologies of Schrenk spruce (Picea schrenkiana Fisch. et Mey.) to climate change at high-and low-elevations of the eastern Tianshan Mountains, Xinjiang, using different detrending methods Author: Affiliation: Institute of Desert Meteorology,China Meteorological Administration,,,, Fund Project: 摘要 | 图/表 | 访问统计 | 参考文献 | 相似文献 | 引证文献 | 资源附件 | 文章评论 摘要:利用新疆东天山高低海拔雪岭云杉（Picea schrenkiana Fisch.et Mey.）年轮样本，采用样条函数法、负指数函数法和区域曲线法3种去趋势方法研制树轮宽度标准化年表，通过分析不同去趋势方法的新疆东天山高低海拔云杉树轮宽度标准化年表特征、年表与气候响应的关系和年表间在不同频域互相关，及其与其它资料对比发现：（1）3种去趋势法对东天山年表质量影响较小，低海拔树轮年表含有更多可靠的气候变化信息。（2）高海拔的雪岭云杉树木径向生长与6-9月平均气温均呈显著正相关，其中标准化树轮年表与7月平均气温相关系数达0.553（P < 0.01，n=58），夏季温度可能是东天山高海拔雪岭云杉径向生长的主要限制因子；低海拔雪岭云杉树木径向生长与春季降水显著正相关，同时与春季平均气温显著负相关，春季高温和缺水共同作用的春旱可能是影响低海拔雪岭云杉径向生长的主导因子，且负指数函数年表对气候响应更敏感。（3）区域曲线法能够保留树轮标准化年表中更多低频信息，但优势不明显。高低海拔标准化年表在低频域相关系数较大，并和历史干旱事件有很好的对应。在东天山高低海拔雪岭云杉的去趋势方法研究中，负指数函数法比样条函数法和区域曲线法更适合。 Abstract:Tree-ring samples from Schrenk spruce (Picea schrenkiana Fisch. et Mey.) were collected from high-and low-elevations of the eastern Tianshan Mountains, Xinjiang. Three detrending methods (smoothing spline, negative exponential function, and regional curve) were used to develop tree-ring width chronologies. The characteristics of these chronologies and the relationship between radial growth and climate change at different elevations were compared. The results showed that (1) detrending method had little effect on the reliability of the chronologies, and the chronologies from low elevations contained more reliable climate change information. (2) The radial growth at high elevations positively correlated with the mean temperature from June to September; the correlation coefficient for the standardized tree-ring chronology and temperature in July was 0.553 (P < 0.01, n=58). The temperature in the summer may be the main limiting factor for the radial growth of these trees at high elevation. Meanwhile, the radial growth of trees at low elevation was positively correlated with precipitation in spring, and negatively correlated with mean temperature in the spring. Higher temperatures and lower precipitation in the spring combined to cause a drought in the early growing season. Furthermore, the drought in the spring limited the radial growth of trees. (3) The regional curve method retained more low-frequency information in the tree-ring standardized chronology, but the advantage was not obvious. There were higher correlation coefficients in the low-frequency of the chronologies between high elevation and low elevations. In summary, the negative exponential function method may be more suitable than the smoothing spline and regional curve methods for dendroclimatology studies on the eastern Tianshan Mountains. 参考文献 相似文献 引证文献

With global warming, the frequency, intensity, and period of extreme climates in more areas will probably increase in the twenty first century. However, the impact of climate extremes on forest vulnerability and the mechanisms by which forests adapt to climate extremes are not clear. The eastern Tianshan Mountains, set within the arid and dry region of Central Asia, is very sensitive to climate change. In this paper, the response of Picea schrenkiana and Larix sibirica to climate fluctuations and their stability were analyzed by Pearson’s correlation based on the observation of interannual change rates of climate indexes in different periods. Additionally, their ecological adaptability to future climate change was explored by regression analysis of climate factors and a selection of master control factors using the Lasso model. We found that the climate has undergone significant changes, especially the temperature, from 1958 to 2012. Around 1985, various extreme climate indexes had obvious abrupt changes. The research results suggested that: (1) the responses of the two tree species to extreme climate changed significantly after the change in temperature; (2) Schrenk spruce was more sensitive than Siberian larch to extreme climate change; and (3) the resistance of Siberian larch was higher than that of Schrenk spruce when faced with climate disturbance events. These results indicate that extreme climate changes will significantly interfere with the trees radial growth. At the same time, scientific management and maintenance measures are taken for different extreme weather events and different tree species.

Drought-related forest growth declines are observed globally in main forest types, especially with repeatedly hot droughts. Therefore, quantifying forest resilience and identifying the factors driving resilience in response to extreme drought with the consideration of atmospheric CO2 fertilization is crucial for the accurate assessment of forest dynamics under current climate change, particularly for the widespread and climate-sensitive spruce forests in the arid Tianshan Mountains, China. Here, we explored the growth response of Schrenk spruce (Picea schrenkiana) to six extreme drought events since 1900, and investigated how tree resilience in pure stands is related to local drought intensity, cambial age (CA), and intrinsic water-use efficiency (iWUE). Specifically, we found that spruce trees had a mean resistance (Rt) value of less than 1, with iWUE contributing less to Rt variation. The results are in agreement with the drought-induced limitations on tree growth in response to increasing CO2, in spite of rising iWUE trends. However, increased iWUE has significant and positive impacts on the recovery (17%) and resilience (15%) of trees, suggesting that increased iWUE enhances the restoration of Schrenk spruce growth after extreme drought events. The growth resilience indices of Schrenk spruce showed that juvenile and adult trees exhibit different strategies to mitigate the drought influences. This study indicated that tree age, climate conditions, and variation in iWUE should be considered simultaneously in drought resilience evaluations to assess forest dynamics objectively in relation to climate change (i.e., drought) and propose appropriate forest management strategies.

The elevation-dependent tree growth patterns and climate–growth relationships were inferred from five tree-ring chronologies of Picea schrenkiana along an altitudinal gradient in the western Tianshan Mountains, northwest China. Schrenk spruce (Picea schrenkiana) is a crucial tree species in the western Tianshan Mountains of northwest China and plays a vital role in local ecosystems; it is of particular importance to assess the growth response of this species to climate in the context of global climate change. In this study, five tree-ring width chronologies of P. schrenkiana were developed along with an altitudinal gradient ranging from 1499 to 2820 m a.s.l. to investigate the radial growth variations and climate–growth relationships at different elevations. The statistical characteristics of tree-ring chronologies, combined with results of correlation matrix, and rotated principal component analysis, suggested that elevation played a crucial role in determining tree growth patterns in the study area. Correlation analyses of tree-ring chronologies with climate variables indicated that climate–growth relationships changed with increasing altitude. Tree growth at the low-elevation sites was primarily limited by moisture availability. With increasing altitude, the importance of precipitation decreased, tree growth at the high-elevation sites was mainly controlled by lower temperature. These results will help understand the growth response of P. schrenkiana to future climate change, and provide critical information for climate reconstructions using this tree species in the study area.

To examine the associations existing between elevation and tree growth, tree-ring width chronologies of Schrenk spruce (&lt;i&gt;Picea schrenkiana&lt;/i&gt;) were developed from sampling sites at different elevations in the Wusun Mountain, Yili region, Xinjiang, northwest China. The radial growth of high-elevation trees was observed to be primarily influenced by meteorological factors in the non-growth season of the previous year. The radial growth of mid-elevation trees was mainly affected by temperature. The radial growth of low-elevation trees was mainly affected by both temperature and relative humidity. About climate change, the radial growth of Schrenk spruce at different elevations showed a non-uniform response to climate variables. Under the condition of intensified drought stress in the future, the forest ecosystem is likely to be greatly affected, and the radial growth of Schrenk spruce at low elevations will be especially inhibited.

Responses to climate change in radial growth of Picea schrenkiana along elevations of the eastern Tianshan Mountains, northwest China

ABSTRACTAim Climate variability may be an important mediating agent of ecosystem dynamics in cold, arid regions such as the central Tianshan Mountains, north‐western China. Tree‐ring chronologies and the age structure of a Schrenk spruce (Picea schrenkiana) forest were developed to examine treeline dynamics in recent decades in relation to climatic variability. Of particular interest was whether tree‐ring growth and population recruitment patterns responded similarly to climate warming.Location The study was conducted in eight stands that ranged from 2500 m to 2750 m a.s.l. near the treeline in the Tianchi Nature Reserve (43°45′−43°59′ N, 88°00′−88°20′ E) in the central Xinjiang Uygur Autonomous Region, northwestern China.Methods Tree‐ring cores were collected and used to develop tree‐ring chronologies. The age of sampled trees was determined from basal cores sampled as close as possible to the ground. Population age structure and recruitment information were obtained using an age–d.b.h. (diameter at breast height) regression from the sampled cores and the d.b.h. measured on all trees in the plots. Ring‐width chronologies and tree age structure were both used to investigate the relationship between treeline dynamics and climate change.Results Comparisons with the climatic records showed that both the radial growth of trees and tree recruitment were influenced positively by temperature and precipitation in the cold high treeline zone, but the patterns of their responses differed. The annual variation in tree rings could be explained largely by the average monthly minimum temperatures during February and August of the current year and by the monthly precipitation of the previous August and January, which had a significant and positive effect on tree radial growth. P. schrenkiana recruitment was influenced mainly by consecutive years of high minimum summer temperatures and high precipitation during spring. Over the last several decades, the treeline did not show an obvious upward shift and new recruitment was rare. Some trees had established at the treeline at least 200 years ago. Recruitment increased until the early 20th century (1910s) but then decreased with poor recruitment over the past several decades (1950–2000).Main conclusions There were strong associations between climatic change and ring‐width patterns, and with recruitments in Schrenk spruce. Average minimum temperatures in February and August, and total precipitation in the previous August and January, had a positive effect on tree‐ring width, and several consecutive years of high minimum summer temperature and spring precipitation was a main factor favouring the establishment of P. schrenkiana following germination within the treeline ecotone. Both dendroclimatology and recruitment analysis were useful and compatible to understand and reconstruct treeline dynamics in the central Tianshan Mountains.

Seasonal snowfall, a sensitive climate factor and the main form of precipitation in arid areas, is important for forest material circulation and surface processes and profoundly impacts litter decomposition and element turnover. However, how the thickness and duration of snow cover affect litter decomposition and element release remain unclear. Thus, to understand the effects of snow on litter decomposition, fiber degradation and their relationships with soil properties, a field litterbag experiment was conducted under no, thin, medium, and thick snow cover in a Schrenk spruce (Picea schrenkiana) forest gap in the Tianshan Mountains. The snow cover period exhibited markedly lower rates of decomposition than the snow-free period. The litter lignin, cellulose and N concentrations in the pregrowing season and middle growing season were significantly higher than those in the deep-freeze period, and the litter C and P concentrations were significantly higher during the onset of the freeze–thaw period, deep-freeze period and thaw period than in the late growing season. The litter cellulose, C and N concentrations were significantly higher under thick snow cover than under no snow cover in most stages. Moreover, the correlations among litter mass, cellulose, lignin/cellulose and soil bulk density varied with snow cover depth. The temporal variations and snow cover depth affected the decomposition process significantly. The former affected lignin, cellulose and P, and the latter affected cellulose, C and N and changed the litter-soil properties relationship. These differences provide references for understanding how winter conditions affect material cycling and other ecological processes under climate change.

Central Asia, with its high mountains, despite its location between Europe and eastern Asia remains a data poor area. However, mountain glaciers are strongly affected by global change and have a wide-ranging impact. A new pollen record over the last 5600 years shows the extension of a dry Artemisia steppe around Lake Issyk-Kul, with a slightly wetter period from 4.5 to 2.7 ka BP (less Ephedra). Picea schrenkiana forest growing on north-facing slopes of the northern Tien Shan Range, are exposed to Westerlies-related precipitation. The pollen record of Picea is therefore a very good marker of wetter and cold conditions. A comparison to a nearby synchronous pollen record at a higher altitude indicates that the whole forest belt moved down, and that it was not a downwards extension of the lower forest limit only. Four cold and humid phases were evidenced over the last 5.6 ka: 5.5 ka, 4.2 ka and following centuries, 3.2 ka and following centuries (before the end of the Bronze Age) and finally the Little Ice Age, with the latter two being more strongly expressed. These climatic changes, in agreement with other Arid Central Asia investigations, corroborate the driving role of the Westerlies far inland. Human activities were more intense in the Mid and Late Bronze Age (4.5–3.2 ka) and in the last 800 years, confirmed by archaeological and historical information. Issyk-Kul and surrounding rich pastureland were most likely an important step in the ancient Silk Road.

Tree-ring-based assessments of drought variability during the past 400 years in the Tianshan mountains, arid Central Asia

Combining tree ring data with remote sensing data can help to gain a deeper understanding of the driving factors that influence vegetation change, identify climate events that lead to vegetation change, and improve the parameters of global vegetation index reconstruction models. However, it is currently not well understood how climate change at different elevations in the central Tianshan Mountains affects radial tree growth and the dynamics of forest canopy growth. We selected Schrenk spruce (Picea schrenkiana) tree core samples from different elevations in the central Tianshan Mountains. We analyzed the relationships of various tree-ring parameters, including tree-ring width, maximum latewood density (MXD), and minimum earlywood density (MID) chronologies, with 1982–2012 GIMMS (Global Inventory Modelling and Mapping Studies) NDVI (Normalized Difference Vegetation Index), 2001–2012 MODIS (moderate resolution imaging spectroradiometer) NDVI, and meteorological data. (1) There were strong correlations between tree-ring width chronologies and the lowest temperatures, especially in July. Tree-ring width chronologies at higher altitudes were positively correlated with temperature; the opposite pattern was observed at lower altitudes. MID chronologies were positively correlated with July temperature in high-altitude areas and mean temperature and highest temperature from May to September in low-altitude areas, and negatively correlated with precipitation during this period. MXD chronologies were mainly negatively correlated with precipitation. MXD chronologies were mainly positively correlated with temperature in April and May. (2) The correlations between MXD chronologies at each sampling point and NDVI in each month of the growing season were strong. Both MID and MXD chronologies were negatively correlated with GIMMS NDVI in July. The overall correlations between tree-ring parameters and MODIS NDVI were stronger than the correlations between tree-ring parameters and GIMMS NDVI in high-altitude areas; the opposite pattern was observed in low-altitude areas. Drought stress may be the main factor affecting tree ring parameters and NDVI. In the future, we should combine tree ring parameters with vegetation index to investigate a larger scale of forests.

Radial growth response of Populus euphratica and Picea schrenkiana to climate extremes on the arid southern slopes of the Tianshan Mountains

Forest ecosystems are strongly impacted by extreme climate, and the age effects of radial growth under drought can provide profound understanding of the adaptation strategy of a tree species to climate change. Schrenk spruce (Picea schrenkiana Fisch. &amp; C.A. Mey) trees of three age groups (young, middle-aged, and old) were collected to establish the tree-ring width chronologies in the eastern Tianshan Mountains of northwestern China. Meanwhile, we analyzed and compared the response and resistance disparities of radial growth to drought in trees of different age groups. The results showed that (1) drought stress caused by increasing temperatures was the main factor limiting the radial growth of Schrenk spruce, (2) the old and young trees were more susceptible to drought stress than the middle-aged trees, as suggested by the responses of Schrenk spruce trees and based on the SPEI (standardized precipitation evapotranspiration index), and (3) the difference of the resistance indexes (resistance, recovery, resilience, and relative resilience) of three age groups to drought supported that the resistance values were in the order middle age &gt; young age &gt; old age, but the recovery, resilience, and relative resilience values were in the order old age &gt; young age &gt; middle age. These results will provide a basis for the ecological restoration and scientific management of dominant coniferous tree species of different age groups in the sub-alpine forest ecosystems of the arid regions under climate change scenarios.